Puzzled at the lack of single unit packs
OK, HVAC contractor is presenting possibilities for an install into a building, it will be an outside unit, single unit that unifies a gas heating unit and an airconditioner. The best single package he can offer up (he’s trapped in the York line) is a furnace with an 80% AFUE—air conditioners a bit better, with a 13 SEER.
Yes, admittedly, it isn’t like we need a huge furnace or more than 2 months of AC a year—but still, how come industry doesn’t have a single unit package with a 90% furnace and a 13 SEER or 14 SEER?
Just had to gripe.
NotAClue
PS
He also can’t figure out how to put an electronic cleaner on the unit, because it will be outside===doesn’t want to put on in the return duct, says they pop and so forth; so it’s going to get a media filter. That’s OK (and probably safer) but you think the industry would have sorted this out too!
Replies
The industry has found that there is no market for such. Typically, when one is interested in 90+ AFUE and/or greater than 13 SEER efficiencies, then there is also the realization that units located outside of the conditioned space nullify most of the gains in efficiency due to the physical design of the equipment. Manufacturers have learned not to indulge idiots.
Electronic air cleaners, BTW, are gizmo's, not used in commercial or institutional applications. This, too, is not a secret to the HVAC equipment manufacturers, though the residential salesmen overlook that fact as they "upsell" you.
OK, I'll bite; why is the location of the unit (not ducting) outside the conditioned space such a drawback?
NotaClue
Take one of these units apart and you'll see why... the steel exterior (great heat conductor), lack of insulation, lots of openings, etc. basically make high-R-value walls impossible. The best I've seen was less than 1" thick of fiberglass, and that's not going to get you far. Insulating them to the same R-value as the rest of the house (i.e. R14+) is pretty much impossible, IMHO.The pathetic insulation is presumably the reason that manufacturers would be relectant to install condensing furnaces in these babies. With no gurantee that the furnace won't go cold in the wintertime, you could have a lot of warranty calls on your hands due to split drain lines and somesuch.One possible approach to make these units more efficient could be a one-piece exterior UV-inhibited XPS/Styro/whatever "house" that slips over the sheet metal to protect it from the elements, heat/sun, etc. How the unit would function under such "insulated" conditions another question. They would probably have to be modified for it or the "leakage" they depend on to cool components inside might be too lacking.In my mind, package units are basically oversized windowshakers. They are cheap to install and therefore popular with tract-home builders who can rent one crane and do dozens of installs in one day. The homeowner pays the price with expensive heating/cooling bills, but by then the builder is long gone. In my mind, one should never tolerate the kinds of holes that these systems put into the thermal envelope of a home.
The unit is very much like ducts, in that economics will allow for some insulation, but not much. If you are trying to cool 75 degree return air to 55 degrees, inside of a semi-sealed, semi-insulated box that is subject to direct solar radiation and outside air temperatures approaching 100 degrees, you can see where the location might have some effect on this process.
The same would apply to heating. Try to heat air from 65 to 105 in minus 10 conditions, and you might not see that true AFUE be reflected in the actual cost to operate.
Bottom line is that the high efficiency, packaged unit market does not support any manufacturer developing the product and bringing it to production. The cost of producing a unit that is well sealed and insulated enough to overcome the enviromental conditions would be greater than all but a very select few would underwrite. I sell these types of units, and 1 out of 50 might be more efficient than the legal, code mandated minimums.
Gentlemen, thank you.
This was very illuminating. I appreciate you taking the time to offer real answers, which are clearly backed by some degree of learned experience.NotAClue
Where are you located? Are you talking abought a heat pump? If so they are only suitable for mild climates. A device that tries to do it all is usually only ok at every thing and not great at anything.